1. Field of Invention
The invention relates generally to indirect lighting fixtures. More particularly, the invention relates to high intensity indirect lighting fixtures which ar aesthetically pleasing in appearance and provide good low angle light distribution.
2. Summary of the Prior Art
Luminaires for indirect lighting rely upon the reflection of light from a source by specially shaped reflective means in a manner which directs the peak candlepower of reflected light at low angles so that its subsequent reflection by the ceiling illuminates the room effectively and efficiently. The use of this lifting technique in luminaires adapted for use in offices, large conference rooms, and other environments is well known. Beyond the functional characteristics of such luminaires, however, the consideration of their aesthetic appearance to, and their psychological impact upon, individuals also has been recognized to be important. In the latter regard, the shape of the fixture, the distance at which it is located from the ceiling, and its brightness relative to the illuminated ceiling are among the factors which influence the ultimate success or failure of a particular design in the marketplace.
In some situations, opaque fixtures have met with some success. These fixtures present fixed areas of darkness against the brightness of the surrounding ceiling which in some contexts do not detract from the appearance of the room, nor from the "usability" of the environment. In other situations, opaque fixtures visually tend to make the room appear smaller. This is particularly the case when the fixture is not located in a large room or in a room having a high ceiling. Therefore, they may adversely effect both the room's appearance and its "usability", especially by taller individuals. In the latter situation, it has been found that the illumination of the exterior surface of the luminaire visually tends to "lift" the luminaire, thereby alleviatinq the problem. This solution is optimized when the brightness of the exterior of the luminaire is substantially homogenious and equivalent to that of the surrounding ceiling.
Since relatively precise control of the reflection of light from the source is critical to the success of an indirect lighting fixture, it is customary to form the- reflective elements from highly reflective specular metals. Cost and weight considerations usually dictate that these elements comprise formed thin sheets. Considerations of the effectiveness and efficiency of the light distribution dictate the specific contours given to the reflective surfaces. Accordingly, the exterior shape of the luminaire generally conforms to the contour of the inner reflective surfaces. Such exterior shapes are not necessarily aesthetically pleasing. This has not caused significant problems to luminaire designers, however, because the exterior shape of the luminaire need not effect the reflective interior contour of the reflective elements. It will be understood that either additional material may be added selectively to the exterior surface of the reflective elements, or an additional element, such as a dome, may surround the reflective elements to provide the desired aesthetically pleasing exterior shape.
The illumination of the exterior surface of the luminaire is not accomplished as easily. It, of course, is possible to provide separate lighting means between the exterior of the reflective elements and a outer translucent member to illuminate the exterior of the luminaire, but that alternative is cumbersome and costly. Designers in the art, therefore, have searched for ways to utilize some of the light from the source to provide the desired illumination of the exterior without significant adverse effect upon the indirect lighting characteristics of the device.
One alternative for achieving this goal is the provision of holes in the reflective member surrounding the light source. Extreme care must be taken in the placement of such holes because the indirect lighting capabilities of the device are easily compromised. Further, in this alternative bright spots or areas on the exterior surface of a translucent member surrounding the reflective member are to be expected. Such bright spots or areas detract from the overall appearance of the luminaire, and are to be avoided. In another alternative, the reflective elements may be made from materials which reflect some incident light, while allowing the remainder to diffuse therethough. These materials are generally deemed unsatisfactory for use in the formation of the reflective elements of an indirect lighting system because the amount of light reflected is not great enough for effective and efficient indirect lighting. In addition, since the concentrations of light rays impinging upon the reflective elements are not the same over the entire reflective surface, it can reasonably be expected that the exterior of a luminaire constructed of such alternative materials will display undesireable bright spots or areas. In yet another alternative, a small amount of the light leaving the open end of the reflective member adjacent its outer edge may be redirected into a gap between the reflective member and an outer translucent member. This alternative has the benefit that the indirect lighting characteristics of the device are not seriously compromised by the redirection of small quantities of light from the periphery of the light distribution directed at the ceiling. The symmetrical qeometry of the luminaire, however, is generally such that illumination of the central area of the outer translucent member by such reflected light will be prevented by the sides of the reflective member. Therefore, the central area will remain dark in comparison to the outer area. This dark area detracts from the appearance of the device just as bright spots or areas do, and should be avoided.
It further has been suggested that the alternative just described may be combined with the provision of an axial hole located in the bottom of the reflective member to allow illumination of the central area of the surrounding translucent member. In this suggestion, the outer translucent member comprises a pair of nested upwardly opening translucent domes surrounding the upwardly opening reflective member in an attempt to even out the exterior illumination. Also, a reflective element of the same dimensions as the hole is suspended between the hole and the horizontally located light source in an attempt to maintain the effectiveness of the indirect lighting capabilities of the device. The resulting illumination of the exterior of the outer dome is not homogeneous and does not match the brightness of the surrounding ceiling. Rather, the appearance is a comparatively brightly illuminated central area surrounded by a dimly illuminated outer area. This visual effect is an improvement over the opaque structures, but the visual "lift" it provides to the device is not totally satisfactory.